This idea is admittedly half-baked at this point, but tell me what you think about what I have so far:
What if the mission options we got from contacts, etc gave us a choice of "Do mission A because it will get you a lot of experience" versus "Do mission B because it will get you a lot of IGC."
Maybe mission A gives NO IGC (like the mobs don't even drop it), or maybe just really LOW IGC returns as compared to everything else.
Similarly the IGC missions would give no XP for defeating mobs, none at the end, etc. or maybe just really pathetic rates of return in comparison.
If this were the case, I think we'd all do mostly XP missions until we got to the cap then mostly IGC missions after that.
Okay, but what if crafting items required you to do XP missions. And by that I mean, you queue up an item you want to craft (after acquiring the salvage and so forth to actually do it) then you have to "work" to get the item done, and your "work" progress is measured in XP gained (or XP that would have been gained, if at the level cap) while the item is enqueued. Then once you've done enough XP missions, your item is fully "cooked" and you get it.
This would cause people to do mostly XP missions when leveling up a toon (but probably not XP exclusively, as you'd wany IGC to slot stuff into your powers as you go along, like SO type stuff), and mostly IGC missions at the cap, but you'd still need to do the XP ones to craft stuff, and maybe that takes up almost half of your missions, or more. The rate of IGC generation would then be tied to how much time people are willing to devote to IGC missions.
And then maybe outdoor street sweeping gives both XP and IGC, but mediocre amounts of both.
And then you could let people use Stars (the real-money-backed currency) to temporarily increase their crafting rate or just "buy" a certain amount of crafting progress or something.
R.S.O. of Phoenix Rising